In semiconductor fabrication, various lithographic processes are extensively used in the course of defining devices and circuit patterns. Depending on the size of the features to be defined, different optical lithographic processes may be used. In a lithographic process, a pattern present on a photomask or reticle may be transferred to a light-sensitive photoresist coating by illuminating the reticle. The light is modulated by the reticle pattern and imaged onto a photoresist-coated wafer.
In conventional lithography, a pellicle is commonly placed on the reticle to protect the reticle from contamination during handling and exposure. The pellicle will thus protect the reticle from unwanted particles which otherwise could negatively impact the fidelity of the pattern transfer to the wafer. As the pellicle remains covering the reticle during exposure, there are stringent requirements on the pellicle in terms of absorption, durability, and particle shielding capabilities, etc.
The membrane of the pellicle may however, due to the radiation and/or chemicals in the process environment, degrade over time. Some degradation may be acceptable but eventually the reticle and the pellicle need to be removed from the lithographic exposure tool to allow replacement of the pellicle. The reticle and the pellicle are typically returned to a mask shop where the pellicle replacement may be performed. This may cause undesired interruptions in the fabrication process. Moreover, while the pellicle is being replaced the reticle surface is exposed to the ambient atmosphere and particles existing in the environment.